troubleshooting
Why doesn't my buzzer make a sound?
Short answer: An active buzzer needs about 20–30 mA and the right polarity. A resistor meant for an LED starves it; wire it straight to 3–5 V with + to the long leg.
See it happen
This is the broken circuit, simulated live. The readout under the board tells you what the parts are doing.
simulating…
What's going on
An active buzzer has a little oscillator circuit inside; give it DC and it makes its own tone. It behaves roughly like a 150 Ω resistor: on 4.5 V it draws about 4.5 ÷ 150 = 30 mA, and it needs most of that to sound.
Put a 10 kΩ resistor in series and Ohm's law does the rest: 4.5 V ÷ 10 150 Ω ≈ 0.44 mA. The buzzer sees a fraction of a volt and stays silent. Even 220 Ω cuts it to about 12 mA and a feeble, quieter tone.
The other silent killer is polarity: active buzzers are one-way parts like LEDs (the simulator's buzzer isn't, so it won't show you that one). The long leg, or the leg marked + on the case, goes toward the battery's + side.
The fix
Wire the buzzer directly: battery + → switch → buzzer + → buzzer − → battery −. No resistor. The internal circuit sets the current.
Rated voltage matters: a "3–5 V" buzzer is happy on 2×AA or 3×AA; a 12 V buzzer is barely audible on either.
simulating…
Also check
- Passive buzzer / piezo disc? Those make no sound on DC at all — they need a signal that switches on and off. That's what a 555 timer is for.
- Backwards. Swap the two legs and try again; nothing is harmed.
- Quiet, not silent? A resistor is still in the loop somewhere, or the battery is tired.